Background: DIELECTRIC BARRIER DISCHARGE (DBD), a source of non-thermal plasma, is used in surface decontamination. Objective: To study the effect of DBD plasma treatment, we evaluated the effect of plasma exposure time on inactivation of Bacillus subtilis. Results: Applying the DBD plasma to the culture of B. subtilis caused complete sterilization of the surface without any thermal effects. In addition, the inactivated colony-forming units increased as the exposure time rises. Conclusion: Considering the low temperature and non-destructive features of this method, it seems that this method is applicable for fast sterilization of resistant bacteria and hospital sensitive instruments.

This paper reports the plasma DISCHARGE analysis of a DIELECTRIC BARRIER DISCHARGE (DBD) source. Helium is used as a working gas. The analysis is performed at fixed working pressure and operating frequency. The investigations are carried out using sinusoidal supply for the generation of DISCHARGEs where two current pulses have been observed with different polarities in one period. A homogeneous type of DISCHARGE has been observed for different operating conditions in this DBD source. Sincein situ diagnostics are not possible due to the small geometries in the used DBD source, the electrical measurements and spectroscopic analysis of the DISCHARGE have been performed to analyse the plasma DISCHARGE. The electrical analysis has been carried out using equivalent electrical circuit model.The plasma density and temperature within the DISCHARGE have been estimated using line ratio technique of the observed visible neutral helium lines. The estimated electron plasma density is found to be in close proximity with the plasma simulation code ‘OOPIC Pro’.

In this study, effects of the variation in the DIELECTRIC BARRIER DISCHARGE’ s (DBD) gap distance and the nature of DIELECTRIC layers which cover both of the reactor electrodes on the electron density, mass fraction of excited argon atoms across the DISCHARGE gap, mean electron energy, ion and electron current density, and electron temperature are investigated at atmospheric pressure. In order to find the optimal reactor gap, the DBD’ s average power consumption is studied. The achievements show that when the value of DIELECTRIC constant is increased from 7. 6 to 10, DISCHARGE gap of 1 mm still demonstrates the maximum power consumption, which can be considered as the optimum DISCHARGE gap. To optimize the characteristics of one-dimensional modeling of DBD system for material treatment, various types of materials with different values of the permittivity [aluminum, glass (quartz) and silicon] are embedded in the DISCHARGE gap between the two electrodes. In this case, the reactor gap is changed from 0. 5 mm to 2 mm, while the DIELECTRIC constant of the DIELECTRIC layers which cover both of the metallic electrodes is assumed to be 10. Compared to the other examined materials, our numerical results illustrate that the treated material with higher value of the relative permittivity (silicon) has greater influences on the variations in the electron density, argon ion density and also total plasma current density than in the values of excited argon atom density, mass fraction of excited argon atoms and also average power consumption.

Non-thermal DIELECTRIC BARRIER DISCHARGE plasma is examined as a method for the ex situ remediation of non-aqueous phase liquid (NAPL)-contaminated soils. A mixture of equal mass concentrations (w/w) of n-decane, n-dodecane and n-hexadecane was used as model NAPL. Two soil types differing with respect to the degree of micro-heterogeneity were artificially polluted by NAPL: a homogeneous silicate sand and a moderately heterogeneous loamy sand. The effect of soil heterogeneity, NAPL concentration and energy density on soil remediation efficiency was investigated by treating NAPL-polluted samples for various treatment times and three NAPL concentrations. The concentration and composition of the residual NAPL in soil were determined with NAPL extraction in dichloromethane and GC-FID analysis, while new oxidized products were identified with attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). The experimental results indicated that the overall NAPL removal efficiency increases rapidly in early times reaching a plateau at late times, where NAPL is removed almost completely. The overall NAPL removal efficiency decreases with its concentration increasing and soil heterogeneity strengthening. The removal efficiency of each NAPL compound is inversely proportional to the number of carbon atoms and consistent with alkane volatility. A potential NAPL degradation mechanism is suggested by accounting for intermediates and final products as quantified by GC-FID and identified by ATR-FTIR.

Ethylene is an undesirable compound for the storage of horticultural products. The traditional fresh-keeping method of fruits and vegetables is refrigeration. However, even in refrigeration environment, ethylene is released by horticultural products themselves or other sources. The residual ethylene can accelerate maturation and corruption of horticultural products and thus should better be wiped away. The technique of DIELECTRIC BARRIER DISCHARGE was applied to decompose ethylene. Under electric DISCHARGE, many energetic and highly reactive species can be produced, which can react with and decompose the chemical compounds in contact with them. In this study, the efficiency of ethylene removal using DIELECTRIC BARRIER DISCHARGE reactor was studied. Ethylene removal rates were affected by many factors, such as gas DISCHARGE gap, wire distance, flow rate, ethylene initial concentration and humidity. The kinetics of ethylene removal was studied. To disintegrate ethylene, the optimal DISCHARGE gap was 3 mm, wire distance 0.5 mm, gas flow rate 3.5 L min-1 and humidity 61 %. Two kinetics models were selected for ethylene decomposition, and experimental results could fit the model with a maximum absolute error of 4 %. With optimal DISCHARGE condition, ethylene can totally be removed. In the future, decomposition of ethylene by DIELECTRIC BARRIER DISCHARGE technology will be a promising method to keep fruits and vegetables fresh.